Skip to main content

Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

See other formats

52                                 ALASKAN GLACIER STUDIES
says "the Malaspina Glacier has shrunk away from the hills, and has left a moraine along their sides. Nevertheless, at one place, at an angle formed by a spur of the hills, the glacier is pushing up against the side of the hills and is crushing down the scrub trees and beautiful flowers. So fast is it doing this, that branches of alder, partially covered with stones and quite alive, are peeping forth from under the debris and protesting against the encroachment of the ice. This debris consists for the most part, not of stones brought along upon the surface of the ice, but of an old moraine, which is being overwhelmed and crushed. I believe that this ice is sliding and swelling over the older ice below so that it can have little or no effect upon the Malaspina Glacier taken as a whole. There are no signs along the edge of the latter down by the mouth of the Yahts6-tah, that it is either advancing or receding There are no piles of stones left behind to indicate its retreat, and no trees crushed down to show its advances."
The upper parts of Agassiz and Seward Glaciers, apparently normally crevassed because of more rapid movement, have been vividly described by Russell and by Abruzzi. Seward Glacier (PI. XI), perhaps the largest valley glacier in North America, with its known length of 25 miles and unknown extension of perhaps 25 miles more, its average width of 8 to 6 miles and its scores of great tributaries, is of especial interest as it is the largest tributary of the Malaspina.
In 1890 Russell described the Seward Glacier within its mountain valley rather fully,1 making measurements of its rate of movement which seemed to be about 20 feet a day in the central part of the ice stream.
Seven years later the Abruzzi expedition traversed parts of Seward Glacier, taking many splendid photographs which will be of value for detennining future conditions in Seward Glacier, and noting especially8 a greater amount of crevassing than in 1890. The motion, however, was apparently slower in 1897 than the rate measured by Russell for Filippi calls attention to the fact that "Mr. Russell and his fellow-explorer, Mr. Kerr, both relate how seracs frequently crashed down with such force as to shake the ice under their feet, and they add that almost incessant reports and rumblings were produced by the rolling and shattering of the fallen rocks. Nothing of the kind was observed by ourselves during the days we spent on and about the Seward. The glacier was always perfectly quiet; only now and then a solitary stone would come down, or a fragment of serac would drop into a crevasse with a dull thud." A possible interpretation of the greater crevassing but slower movement in 1897 would involve a period of more rapid movement just beginning in 1890 (Russell unfortunately did not go back this way in 1891), but which had ceased before 1897, although the glacier was still severely crevassed the latter year as a result of it.
In 1911 Seward Glacier was easily crossed near Pinnacle Pass by a Boundary Survey party. Their photographs indicate that the crevassing was about the same as in 1897.
In 1891 Russell observed near Point Manby evidence of a former advance of the Malaspina border due to earlier renewal of activity of either Seward or Marvine lobe.3 "A recent advance of the glacier had cut scores of spruce trees short off and piled them in confused heaps. After this advance the ice retreated, leaving the surface strewn with an irregular -sheet of boulders and stones. . . . The glacier during its advance
i Nat. Geog. Mag., Vol. IH, 1891. pp. 177-180.
* The Ascent of ML St. Elias, London, 1900, p. 111.
 13th Ann. Sept., U. S. Geol. Survey, 1894, p. 68,